Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 311655
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1055 AM MDT SUN MAY 31 2015

.UPDATE...
ISSUED AT 1033 AM MDT SUN MAY 31 2015

THE MAIN CONCERN FOR TODAY IS THE POTENTIAL FOR THUNDERSTORMS THIS
AFTERNOON MAINLY ALONG AND EAST OF THE LARAMIE RANGE.

LATEST VISIBLE LOOP AND OBSERVATIONS WERE SHOWING DRIER AIR
BUILDING OVER THE CHEYENNE RIDGE NEAR THE PROXIMITY OF THE SURFACE
LOW NEAR THE CO/WY BORDER. IN FACT...THE VWP WAS SHOWING THE
NORTHWEST FLOW REGIME INCREASING IN DEPTH WHICH WILL FAVOR VERY
WARM CONDITIONS WITH HIGHS IN CHEYENNE POSSIBLY CLIMBING TO NEAR
80 DEGREES WHICH IS SIMILAR TO ADJACENT LOWER ELEVATIONS.
HOWEVER...IT APPEARS LIKE THERE IS A GOOD UPSLOPE COMPONENT ALONG
THE LARAMIE RANGE JUST NORTH OF THE CHEYENNE RIDGE STRETCHING TO
SOUTHERN CONVERSE COUNTY WITH DEWPOINTS STILL IN THE 50S. THIS IS
A FAVORABLE REGIME TO GET THUNDERSTORMS GOING ALONG THE NORTHERN
LARAMIE RANGE THIS AFTERNOON. ONCE THESE STORMS DO GET
GOING...THEY WILL MOST LIKELY DIVE SOUTHEAST AND AFFECT AREAS
MAINLY EAST OF CHEYENNE...BUT IF THE CHEYENNE AREA DOES SEE A
STORM IT MAY PRODUCE GUSTY WINDS DUE TO A DEEP/DRY BOUNDARY LAYER.
SOME OF THE STORMS WILL BE CAPABLE OF PRODUCING SOME MARGINAL HAIL
(LESS THAN ONE INCH) AND GUSTY WINDS UP TO 50 MPH. HOWEVER...ONE
CANNOT RULE OUT A TOKEN STORM OR TWO BECOMING SEVERE WITH THE MAIN
THREAT BEING GUSTY WINDS. MOST OF THE THUNDERSTORMS SHOULD DIVE
SOUTHEAST INTO THE COLORADO BY EVENING.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 310 AM MDT SUN MAY 31 2015

NARROW LINE OF LIGHT SHOWERS PROGRESSING OVER SE WYOMING INTO THE
NORTHERN PANHANDLE EARLY THIS MORNING AS A MINOR SHORTWAVE MOVES
ACROSS THE AREA. EXPECT THIS TO MOVE OUT OF THE CWA WITHIN A FEW
HOURS WITH SOME CLEARING BEHIND THIS WAVE.

UPPER RIDGING WILL AMPLIFY SOME OVER THE REGION TODAY AND TONIGHT
WITH WARMING MID LEVEL TEMPS. TEMPS SHOULD WARM WELL INTO THE 70S
ACROSS THE PLAINS OF THE CWA TODAY WITH SOME LOWER 80S OVER THE
PANHANDLE AS WELL. NEXT IMPULSE WILL MOVE ACROSS THE REGION THIS
AFTERNOON AND SHOULD INTERACT WITH CAPES FROM ABOUT 500-1000 J/KG
MAINLY OVER THE PLAINS TO SET OFF SCTD SHOWERS AND TSTMS. A FEW
STRONGER STORMS POSSIBLE WITH HAIL THE MAIN THREAT. ACTIVITY WILL
DIMINISH DURING THE EVENING AS THE SHORTWAVE DROPS SOUTHEAST OVER
THE CENTRAL PLAINS. ON MONDAY THE UPPER RIDGE AXIS SHOULD EDGE
EAST ACROSS THE CWA WHILE THE NEXT SHORTWAVE MOVES THROUGH IT AND
OVER THE HIGH PLAINS BY MONDAY EVENING. SHOULD SEE ANOTHER ROUND
OF SCTD SHOWERS AND TSTMS DEVELOP IN THE AFTERNOON ACROSS THE MTNS
INTO THE PLAINS. SOMEWHAT BETTER MOISTURE WILL CONTRIBUTE TO
HIGHER CAPE VALUES ESPECIALLY OVER THE PANHANDLE WHERE VALUES IN
EXCESS OF 2500 J/KG PROGGED. SHEAR WILL BE SOMEWHAT LACKING
HOWEVER BUT SOME STRONG STORMS LIKELY. AGAIN THIS ACTIVITY SHOULD
WANE DURING THE EVENING. LESS CONVECTIVE ACTIVITY EXPECTED FOR
TUESDAY AS A SFC TROF MOVES INTO THE PLAINS BUT THIS TROF SHOULD
SERVE TO FOCUS CONVECTION TUESDAY AFTERNOON OVER THE PANHANDLE
WITH PRETTY GOOD CAPES PROGGED JUST EAST OF THE CWA.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 310 AM MDT SUN MAY 31 2015

GFS/ECM/GEM ARE ALL IN GOOD AGREEMENT WITH DEEP TROUGHING OVER THE
WESTERN CONUS THROUGH THE EXTENDED PERIOD. THIS WILL RESULT IN MOIST
SOUTHWEST FLOW ALOFT OVER THE CWA THROUGH MID TO LATE WEEK....LIKELY
YIELDING AN ACTIVE PATTERN FOR CONVECTION. PERSISTENT EAST-SOUTHEAST
LLVL UPSLOPE WILL HELP TO MAINTAIN DEW POINTS IN THE 50S TO THE EAST
OF THE LARAMIE RANGE. BOTH THE GFS AND ECMWF SHOW SFC CAPE VALUES OF
1500-3000 J/KG EACH AFTN FROM WED ONWARD...ALONG WITH 0-6 KILOMETER
SHEAR AVERAGING BETWEEN 30 AND 40 KTS. WHILE CONVECTIVE COVERAGE MAY
BE LIMITED BY PERIODS OF SHORTWAVE RIDGING...FAVORABLE DIVERGENCE AT
H25 AND LLVL CONVERGENCE WILL HELP PROMOTE AT LEAST ISOLATED/WIDELY
SCATTERED SHOWERS AND THUNDERSTORMS. CONFIDENCE IS FAIRLY HIGH THAT
SEVERE STORMS WILL OCCUR IN THIS PATTERN. DAYTIME HIGH TEMPERATURES
WILL REMAIN NEAR SEASONAL NORMS WITH PLENTIFUL CLOUDS EXPECTED EACH
AFTERNOON/EVE. THIS...COMBINED WITH COOL UPSLOPE...SUGGESTS HIGHS A
FEW DEGREES BELOW CURRENT MOS GUIDANCE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 537 AM MDT SUN MAY 31 2015

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER
SOUTHEAST WY AND THE WESTERN NE PANHANDLE AFTER 18Z. A FEW STRONG
STORMS ARE POSSIBLE WITH GUSTY/ERRATIC WINDS...SMALL HAIL...AND
BRIEF HEAVY RAIN. OVERALL CONDITIONS SHOULD REMAIN VFR THROUGH
MUCH OF THE TAF PERIOD. HOWEVER...BRIEF MVFR CIGS/VSBYS ARE QUITE
POSSIBLE BENEATH ANY HEAVIER STORMS.


&&

.FIRE WEATHER...
ISSUED AT 310 AM MDT SUN MAY 31 2015

WARMER TEMPERATURES CAN BE EXPECTED ACROSS THE DISTRICTS TODAY
WITH WARM TEMPERATURES EXPECTED TO HOLD THROUGH THE WEEK. THERE
WILL BE THE FAIRLY TYPICAL LATE DAY SCATTERED SHOWERS AND
THUNDERSTORMS MOST DAYS THIS WEEK AS WEAK IMPULSES INTERACT WITH
AFTERNOON AND EVENING INSTABILITY.

&&

.HYDROLOGY...
ISSUED AT 310 AM MDT SUN MAY 31 2015

THE LARAMIE AND NORTH PLATTE RIVERS OVER THE PLAINS ARE FORECAST
TO BE STEADY OR SLOWLY FALL OVER THE NEXT COUPLE DAYS AS EXCESS
WATER FROM RAINFALL MOVES ON DOWNSTREAM. FOR THE UPPER LARAMIE
RIVER AND THE UPPER NORTH PLATTE RIVER WARMING TEMPS WILL INCREASE
SNOWMELT WHICH WILL IN TURN BRING THESE RIVER SECTIONS TOWARDS OR
EVEN EXCEEDING BANKFULL EARLY IN THE WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&

$$

UPDATE...REC
SHORT TERM...RE
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...RE
HYDROLOGY...RE



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